Recent advance in microarray/oligonucleotide array technology has enabled exhaustive analysis of gene expression. It is predicted that a cancer could also be assessed for its pathological conditions by microarray profiling data for the gene. Actually in leukemia, it is reportedly possible to classify leukemia by gene expression profiles. By clarifying the gene expression profile of each cancerous tissue and accumulating its classification, it is considered possible to predict response to a particular cancer therapy or discover a novel drug development target protein for a particular cancer. Specifically, where enhanced expression of a certain protein is observed in a certain cancer, it becomes possible to induce an anti-tumor activity in patients newly diagnosed to be antigen positive, by means of (i) reducing its expression level, (ii) suppressing its function, (iii) eliciting immune response of host to the protein, etc. At the same time, patients diagnosed to be antigen negative can immediately switch over to another cancer therapy, assuming to eliminate any concern of imposing a superfluous burden on patients. As such, it is expected that the expression profile analysis would greatly contribute to molecular diagnosis of a cancer and development of molecular target-based drugs.
Meanwhile, FLJ20539 gene (GenBank Accession No. AK000546) is a gene cloned from a library derived from the human gastric cancer cell line KATOIII and encodes a protein consisting of 774 amino acids (GenBank Accession No. BAA91245). The FLJ13515 gene (GenBank Accession No. AK023577) is a gene cloned from a human placenta-derived library and encodes a protein consisting of 639 amino acids (GenBank Accession No. BAB14613). This protein has an amino acid sequence corresponding to the 136-774 amino acid sequence of a protein encoded by the FLJ20539 gene, in which the amino acid at position 440 is replaced from glutamic acid to lysine. Furthermore, a mouse gene (GenBank Accession No. BC006896) showing homology to these 2 human genes is cloned from a mouse breast cancer tissue-derived library and encoded by a protein consisting of 1018 amino acids (GenBank Accession No. AAH06896). This mouse gene has homology of about 83% in the base sequence and about 86% in the amino acid sequence, to the FLJ13515 gene.
A safe drug capable of targeting the molecule specifically expressed in cancer cells to induce growth inhibition of the cancer cells has been earnestly desired.